Disclosed herein is a vehicle seat, and particularly, a vehicle seat which reduces an impact of rear end collision and simplifies a peripheral structure of a side frame.
In general, in a case where a so-called rear end collision occurs when a rear portion of an automobile or the like collides with something or the rear portion thereof largely collides with something when traveling rearward, a head of an occupant sitting on a seat is suddenly inclined backward by the inertia force, and hence some stress may occur on the occupant's neck.
For this reason, the vehicle seat of the automobile or the like is conventionally equipped with a headrest which is provided above a seat back and receives the occupant's head from the rear side so that the occupant's head or neck is protected from an impact load generated by the rear end collision and the stress on the neck is reduced.
However, the headrest alone may not reduce the impact load applied to the human body. Then, when a gap between the occupant's head and the headrest is not promptly removed during the rear end collision, it is difficult to sufficiently reduce the impact applied to the neck.
In order to solve such a problem, there is known a technique of effectively reducing an impact by sufficiently sinking an occupant into a seat back in the event of rear end collision, where a movable link member is disposed in a side frame of a seat back frame provided with a pressure receiving member which receives the occupant's load, and a pressure receiving member is attached to the link member through a joint member (refer to Japanese Patent Document No. 2009-023517 A (“the '517 Document”)).
The seat back frame disclosed in the '517 Document may sufficiently sink the occupant into the seat back frame in a manner such that the pressure receiving member receives the occupant's rearward movement in the event of the rear end collision so that the link member pivots. Then, since the link member is provided with a biasing element and the pivoting of the pressure receiving member is normally suppressed by the biasing element, the sensation of sitting on the seat is not degraded. Then, a plurality of stoppers that adjust the movement allowing range of the link member are arranged around the link member, and hence the range of sinking the occupant may be adjusted.
In the technique of The '517 Document, the stoppers are provided at two positions on the side frame. Among the two stoppers, the first stopper is used to regulate the link member at the initial position before the pivoting and the second stopper is used to regulate the link member at the stop position after the pivoting.
Accordingly, in the seat back frame disclosed in The '517 Document, a plurality of members are intensively arranged around the side frame. In this way, when many members are arranged around the side frame, the structure becomes complex due to the large number of arranged components, and hence a problem arises in that some time is taken for the attachment operation during assembly. Further, when the stoppers are provided in the side frame, there is a need to ensure a comparatively large space around the link member, and hence a problem arises in that a degree in freedom in design is degraded.
Further, in the seat back frame disclosed in The '517 Document, the pressure receiving member receives the occupant's rearward movement in the event of the rear end collision, and the joint member (the wire) attached to the pressure receiving member also receives the rearward tension. Then, since the joint member receives the rearward tension, the link member which is attached to the side of the side frame in the joint member pivots.
Then, in the technique disclosed in The '517 Document, the joint member is hooked to a hole which is formed by an elongated hole provided in the link member. Then, when the rear end collision occurs, the pressure receiving member receives a large load for a relatively short time by the occupant's rearward movement, and the load is transmitted to the link member through the joint member. Accordingly, when the occupant's rearward movement is received in the event of the rear end collision, the joint member hooked to the link member pivots, and hence a problem arises in that the hooked portion of the joint member separates from the hole of the link member.
The joint member and the link member may not be completely anchor-jointed to each other since the link member needs to pivot in the event of the rear end collision, and the joint member needs to slide on the link member. Accordingly, the joint member may be swaged to the link member, but since the number of components increases, the workability during the attachment operation is degraded. Accordingly, there has been a demand for a technique of preventing the easy separation of the joint member by suppressing the pivoting of the joint member attached to the impact reduction member (the link member) with a simple configuration.